102 THE BIEDS OP MONGOLIA ETC. 



althouo-h we were at the latter place in the end of July, many young birds 

 were still unable to fly. 



In Tsaidam it stops for the cold season on the unfrozen streams and 

 marshes. The migration there took place about the 13th of February. 



At Koko-nor, where only very few migrants pass, we did not see 

 a single flock of Anas boschas consisting of twenty or thirty in number, 

 although it occurs there. 



In Ussuri country Anas boschas is the commonest species, and is the 

 most numerous Duck not only during the breeding-season but also during 

 migration. About Lake Hanka the earhest migrants appear early in March ; 

 but the principal migration takes place in the latter part of that month and 

 early in April, and at this time the numbers are astonishingly great. 



For whole days, but principally in the mornings and evenings, one can 

 see everywhere large flocks of Ducks flying in a northerly direction. They 

 stop in the middle of the day, for a short time only, in order to feed and rest 

 as quickly as possible, and then again resume their flight. Storms or cold 

 weather force them to interrupt their journeys, in which case they usually 

 settle down in some locality to wait for fairer weather. 



We got the same results from our observations on Dalai-nor and in 

 Mongolia, where, during the cold and stormy weather, enormous flocks of 

 Geese and Ducks assemble ; but on the appearance of the first clear day 

 every lake becomes quite desolate, until the arrival of fresh birds. 



In Monvoha, as also about Lake Hanka, the wild Ducks leave in flocks 

 consisting of the present species, or also in company with others ; and on 

 several occasions we observed flocks of drakes only. 



In Ussuri country it begins breeding about the middle of April ; but 

 during that time we have here very often fires over large districts covered 

 by grass. These tires sometimes last all May, and even as late as the middle 

 of June. They destroy a great number of Ducks' nests, which explains the 

 late broods met with so often in Ussuri country and about Lake Hanka, 

 where we saw young in down late in June or even in the early part of July ; 



